Could Genetics Help Us Understand Mass Killers?

Wayne Carver, the state's chief medical examiner, asked geneticists at the University of Connecticut to join the investigation into the Dec. 14 killings at Sandy Hook Elementary School in Newtown. A retired FBI profiler said in response, "I think it's great to consider if there's something here that would help people understand this behavior."

Where's the harm? What could go wrong?

In principle, genetics could pinpoint a biological defect that could explain the rampage of Adam Lanza, who shot students, school staff members, his mother and himself.

"Is there any identifiable disease associated with this behavior?" Carver asked. Of course there is. The first hit on this fishing expedition was Asperger's syndrome, with which Adam Lanza was alleged to have been diagnosed as a child. Consensus quickly emerged that Asperger's does not predispose one toward violent behavior — the autism spectrum was, then, a genetic red herring. But the genetic investigation continues, and the likelihood of finding some correlated disease or syndrome is high. Here are some things they might find:

Other personality disorders. Lanza was "a nerd," quiet, shy, smart and he favored the dark, eerie aesthetic of Goth culture. So many kids fit this profile it is almost inconceivable that they don't have some genetic markers in common.

A relative with a history of violence. A study published last year using the time-honored method of studying twins claimed to show that criminal behavior can be predicted by genetics. Indeed, family identity was briefly implicated in the Sandy Hook massacre — for a few hours Lanza's brother was thought to be the shooter — but that turned out to be another red herring. A detailed analysis of Lanza's pedigree, however, might produce antisocial ancestors, which could aid in post-hoc prediction.

The "violent-drunk" gene. A form of a serotonin receptor (HTR2B) is associated with violent impulsive behavior, if the bearer is male and has been drinking alcohol. A study published in 2010 triggered wide speculation that this gene was responsible for that burly jerk at the bar who keeps picking fights late in the fourth quarter of the football game.

The "warrior" gene. A particular form of the neurotransmitter monoamine oxidase (MAOA-L) has been linked to a variety of aggressive behaviors and impulsiveness.

A sophisticated genetic explanation, however, would not feature a single "massacre" gene. It would involve a complex profile — a constellation of alleles, or particular forms of a gene, which, acting in combination and in certain environments, give a high risk of violent action.

Genetic science is well past the days of single genes for complex behaviors. The news media, however, are not. One blog asked, "Did Adam Lanza's genes make him a murderer?" The impression persists that,if we boil it down far enough, complex, nuanced, 21st-century genetics can provide our craving for simple, fundamental explanations as to why the incomprehensible continues to happen.

Although in Lanza's case the only benefit of genetic analysis is the potential for better understanding after the fact, the long-term goals of such a study are prediction and prevention. These of course are also the goals of modern genetic medicine. We already screen for several dozen diseases at birth; psychiatric conditions and syndromes could easily become part of such a program. As antisocial behavior is increasingly medicalized, then, genetic surveillance logically and easily expands from hypertension to psychosis to school shootings.

Should genetic risk factors be identified, steps could theoretically be taken to avert another massacre. These could include lifetime surveillance (perhaps merely informally, by family members, teachers and employers) counseling, medication and, in cases of extreme likelihood, pre-emptive institutionalization. Chilling steps toward genetic prevention, then, needn't involve science-fiction scenarios involving prenatal diagnosis and gene therapy. They could be accomplished by means of existing conditions of law and sentiment.

Dystopian science fiction movies such as "Gattaca" and "Minority Report" sensationalize troubling visions of the biological control of social behavior. Our genetic future will not be so dramatic; nor — more's the pity — will the actors look like Uma Thurman or Tom Cruise. The future creeps up on you mundanely, through innumerable small steps, each a natural, easy and hopefully compassionate consequence of the last.

Nathaniel Comfort is a historian of genetics at Johns Hopkins University. His latest book is "The Science of Human Perfection: How Genes Became the Heart of American Medicine."